The primary objective of this proposal is to develop the avian knee as a model system for the study of the pathobiology of acquired defects of the temporomandibular joint (TMJ). Osteoarthrosis of the TMJ probably affects almost 40 percent of patients with TMJ pain. Osteoarthrosis of the TMJ has not been successfully induced experimentally and its pathogenesis has not been described. A model system is needed to provide base line data (e.g. progression and repair) of degenerative changes in the histologically uncommon articular cartilage of the TMJ. To accomplish this task, the validity of the model will be tested by comparing the response of the articular cartilage of the avian knee, the mammalian TMJ and the mammalian knee to a chemical insult routinely used to experimentally induce rheumatoid-like arthritidies in hyaline cartilage joints. A congruence of histological and histochemical responses between the avian knee and the mammalian TMJ would strongly support the use of the avian knee as a viable model system. Preliminary experiments (see Preliminary Studies) and a similarity of histological and histochemical features suggests that such a congruence exists. The developed model system will allow examination of the pathogenesis of osteoarthrosis in the connective tissue covered joint cartilage. Degenerative changes will be induced biomechanically through the use of two methods of demonstrated effectiveness in the mammalian knee. Avian knees will be subjected to both impact loading and abnormal vector loading (excision of the anterior cruciate ligament). Finally, the avian knee will be subjected to accelerated wear (via treadmill) to simulate premature aging. Results will be standardized by examining the alterations in the articular cartilages using standard histological stains (Hematoxylin and Eosin, Mallory's) and specific glycosaminoglycans (GAC) stains (Safranin-O and Alcian Blue-critical electrolyte concentration). Comparisons will be made between the results of this last experiment and the previous one (impact loading) to examine these two frequently discussed causative phenomena. Successful completion of this proposal will lead to new insights through which more precise therapeutic regimens can be devised.